One of the features of this invention is to provide a heat exchanger device wherein heat in a waste gas that contains precipitable vaporized and entrained solids is conducted to a second cooler gas such as make-up air for a room or the like with the solids being precipitated in the passages of the heat exchanger through which they are conducted. Selectively energizable heating means are provided in heat transmitting relationship with the contaminated gas passages for heat liquifying these contaminants as an aid in their removal such as by gravity flow from the surfaces on which the contaminants are deposited.
The most pertinent prior art of which applicant is aware are the following U.S. Pat. Nos.: Re. 16,807; 1,790,205; 1,805,657; 3,464,224 and 3,827,343. None of these prior art patents disclose the invention features claimed herein.